Spray coating

Abstract

Provided is a spray coating that is disposed on an inner peripheral surface of a cylinder bore of a cylinder block made of aluminum or an aluminum alloy. The spray coating contains 0.005% to 0.14% by mass of carbon, 0.01% to 3.0% by mass of nickel 10% to 20.5% by mass of chromium, 0.05% to 1.5% by mass of silicon, and a balance containing iron and inevitable impurities. The spray coating has a composition that forms a martensite+ferrite (M+F) region in the Schaeffler diagram, and a composition in which a nickel equivalent (NiE) and a chromium equivalent (CrE) satisfy a relationship expressed by the following Formulae (1): NiE≤0.95 CrE−8.59, (2): NiE≤4.1, and (3): CrE≥10. The spray coating has a two-phase structure formed of a martensite phase and a ferrite phase.

The invention claimed is: 
     
       1. A cylinder block comprising:
 a cylinder bore having an inner peripheral surface; and 
 a spray coating disposed on the inner peripheral surface of the cylinder bore; wherein: 
 the cylinder block is made of aluminum or an aluminum alloy; 
 the spray coating contains:
 0.005% to 0.07% by mass of carbon, 
 0.01% to 3.0% by mass of nickel, 
 10% to 15.5% by mass of chromium, 
 0.05% to 1.5% by mass of silicon, and 
 a balance containing iron and inevitable impurities; 
 
 the spray coating has a composition that forms a martensite+ferrite region in a Schaeffler diagram, and in which a nickel equivalent (NiE) and a chromium equivalent (CrE) in the Schaeffler diagram satisfy a relationship expressed by the following Formulae (1) to (3)
   NiE≤0.95CrE−8.59  (1),
 
   NiE≤4.1  (2), and
 
   CrE≥10  (3);
 
 
 the spray coating has a two-phase structure formed of a martensite phase and a ferrite phase; and 
 the spray coating has a surface porosity of 2.7% or less. 
 
     
     
       2. The cylinder block according to  claim 1 , wherein the spray coating has a composition in which the chromium equivalent (CrE) in the Schaeffler diagram satisfies a relationship expressed by the following Formula (3′)
   CrE≥11.5  (3′).
 
 
     
     
       3. The cylinder block according to  claim 1 , wherein the spray coating has a composition in which the nickel equivalent (NiE) in the Schaeffler diagram satisfies a relationship expressed by the following Formula (2′)
   0.4≤NiE≤4.1  (2′).
 
 
     
     
       4. The cylinder block according to  claim 1 , wherein the spray coating has a composition in which the nickel equivalent (NiE) and the chromium equivalent (CrE) in the Schaeffler diagram satisfy a relationship expressed by the following Formula (1′)
   NiE≤0.93CrE−10.18  (1′).
 
 
     
     
       5. The cylinder block according to  claim 1 , wherein the spray coating contains 11.5% to 15.5% by mass of chromium, and has a composition in which the chromium equivalent (CrE) in the Schaeffler diagram satisfies a relationship expressed by the following Formula (3′)
   CrE≥11.5  (3′).
 
 
     
     
       6. The cylinder block according to  claim 1 , wherein the spray coating contains 11.5% to 15.5% by mass of chromium, and has a composition in which the chromium equivalent (CrE) in the Schaeffler diagram satisfies a relationship expressed by the following Formula (3″)
   11.5≤CrE≤15.5  (3″).
 
 
     
     
       7. The cylinder block according to  claim 1 , wherein the spray coating contains 0.005% to 0.07% by mass of carbon, 0.01% to 0.6% by mass of nickel, 11.5% to 15.5% by mass of chromium, 0.05% to 0.5% by mass of silicon; and has a composition in which the nickel equivalent (NiE) in the Schaeffler diagram satisfies a relationship expressed by the following Formula (2″)
   0.4≤NiE≤2.3  (2″).
 
 
     
     
       8. The cylinder block according to  claim 1 , wherein the spray coating further contains manganese and/or molybdenum. 
     
     
       9. The cylinder block according to  claim 1 , wherein the spray coating further comprises 0.2% to 1.2% by mass of manganese and 0.01% to 0.34% by mass of molybdenum. 
     
     
       10. The cylinder block according to  claim 1 , wherein the surface porosity is in a range of 1.05% to 2.7%.